Under the terms of their agreements with the U.S. Postal Service, all Internet postage vendors issue a standard form of electronic postage. The Postal Service developed this postage, called an "Information-Based Indicium," to allow vendors to deliver secure, tamper-proof electronic postage. It includes several different elements:
- A bar code the Postal Service uses to sort mail automatically
- A standard postage value, mail class, and date stamp
- A second, larger bar code that includes an encrypted digital signature to prevent fraud or counterfeiting. This bar code also encodes the destination ZIP code, the amount of postage applied, and the date and time that the postage was applied.
Any standard inkjet, bubblejet or laserjet printer can print Internet postage on a variety of envelopes, labels and mailers all of the encoded information is represented in the bar code itself, not in a special ink or printing process.